Replacement Wings

[reichelt]

Need an education on converting from ragwing to metal wings on a C170. Is there an STC out there that covers the mod. Any issues with the conversion. Will 60's versions of C172 or C175 wings fit. Thanks for the help.

[Bruce Fenstermacher]

The '48 rag wing has a completely different wing than the later 170s and 172s. They are not interchangeable.

Now you may find a metalized '48 170 wing though to tell the truth I've don't recall ever seeing one. What this would be is a stock '48 wing covered in aluminum instead of fabric.

This was a modification done to 140s with both 337 one time approvals and STCs that were available at the time. I wouldn't be surprised if one of the 140 STCs that allowed replacing the fabric with metal also covered the 170. I would also be surprised to find any of those STCs still available today.

What's wrong with the wings you have?

[doug8082a]

I've come across a few metalized 170s in the last few years. I know this was common among the 140, 170, and Stinson crowd in years past. But today, the modern fabric and coatings available really eliminate any need to "metalize" a fabric wing. A metal wing will weigh more and be harder & more expensive to repair.

As Bruce said, the '48 wing is unique to the straight 170 and you can't swap it out for a later 170A/B or 172/175 wing.

If you are recovering a '48 wing, I'd go with an approved fabric covering.

[Bruce Fenstermacher]

It is arguable whether a metalized wing will weigh more than fabric and all the paint.

I remember from my Piper Short Wing forum days this argument came up as much as the MMO discussion. Most of the finding were that in the end they were the same with the metalized versions having a slight advantage of maybe a few pounds less.

I personally would not metalize a wing (or fuselage) today but I wouldn't shy away from a nicely done metalized example either.

[djbaker]

I recently saw a 170 in for a prebuy inspection that had metalized wings. The wings had very unusual inspection ports along the underside of the wing and dented metal on top. I wonder how it could fly. I wondered how it passed annual. It looked like it had been through a demolition derby and won!! Too bad to ruin a good airplane.

[GAHorn]

Don't know about the difference in a fabric versus a metalized straight 170 wing... but when Cessna produced the all-metal 170A the wings lost 20 lbs, according to their data. (No need for internal bracing in an all metal wing.)

[steve grewing]

Here are the two weight and balance entries in my plane records for pre and post wing metalization (is that a real term?):

DATE EMPTY WEIGHT CG USEFUL LOAD DESCRIPTION
2/3/1950 1237.5 37.2 962.5 Installed VHF radio.
3/5/1956 1325 30 875 Metalized wings.

(Note the error in the CG, this was not corrected until 1967.)

I was curious also and did the math on area vs weight of cotton with dope/paint and 0.020" alclad. Difference is about 90 pounds. I'd like to have that 90 pounds of fuel back as I haven't weighed 170 lbs since about the time that cg error was corrected.
Also, my wings still have all the internal braces in place.

Steve

[Bruce Fenstermacher]

Steve were did you get the weight of the fabric, glue and paint?

Like I said over the years this has come up in various conversations and the actual weight difference isn't that much. At 90LBS I would wonder why anyone would do it.

[doug8082a]

There's got to be more to that 90 lbs. than just the wings. My thoughts were that metallized wings would weigh more, but not 90lbs. more.

[GAHorn]

...Also, my wings still have all the internal braces in place.

Steve

I know YOU know it, Steve,...but just to be certain others aren't confused about it.... Metallizing fabric wings does not allow an opportunity to remove internal structure necessary to provide wing stiffness. My earlier comment about an all-metal wing not requiring the internal bracing which fabric wing require was purely in comparison of the 170A/B series wing to the fabric 170 wing.

(The reason a 170A/B airplane has a single wing-strut is because the all metal construction of the wing creates a series of stiff "boxes" which counters against twisting/flexing of the wing. The fabric wing must have both it's forward and rear spars braced against such twisting, as well as it's internal structure of spars/ribs must be braced for stiffness and against collapse from external forces. The need for such bracing being obviated makes the all-metal 170 A/B wings/aluminum-struts about 20 lbs lighter than the fabric wing/dual-steel-struts.)

[Kyle Wolfe]

I learned to fly in my dad's 48 170 back in the 70's. It had been metalized by a company in Colorado. My memory says it was Met-Co Aire. The N number was 3914V. It's owned by a member in Alaska......

[steve grewing]

Bruce,

I did a little research on weight per square foot of grade A cotton and .020 alclad. Calculated the weight of paint/dope/primer less the VOC's as related to how much paint/primer I used to paint my wings. Measured my wings for area and then did the math. The margin of error can't be that great considering the limited quantities. Just the sheet metal is nearly 100 pounds.

I did not believe the comments I had read about the metalized aircraft losing roughly 90 pounds of useful load. But I did after the math.

Steve